Reject non-constructor self types in const-arg tuple-call lowering#157513
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Reject non-constructor self types in const-arg tuple-call lowering#157513Dnreikronos wants to merge 1 commit into
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A braced const argument that is a call, like `Ty<{ Ty::f() }>`, is lowered
as a tuple constructor. When the callee's self type cannot host a
tuple-variant constructor (a struct, union, primitive, or foreign type),
the call is an associated function, not a constructor, and must be wrapped
in a `const { ... }` block.
Detect that from the self type's resolution before lowering it, and emit
the existing "complex const arguments must be placed inside of a `const`
block" diagnostic. A generic struct written without its arguments, as
`tracing`'s logging macros generate, would otherwise produce a spurious
E0107 "missing generics" cascade; a primitive or foreign type would
surface an opaque "invalid base path" error.
Enums, aliases, `Self`, and type parameters are left to constructor
lowering, since each may resolve to an enum.
Add UI tests for struct, union, primitive, and foreign self types, plus
the `const { ... }`-wrapped form that compiles.
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HIR ty lowering was modified cc @fmease |
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Turning on
min_generic_const_argsmakestracingstop compiling. Its logging macros expand a field name to something likeFieldName<{ FieldName::len(stringify!(field)) }>, and under mgca a braced call in const-arg position gets lowered as a tuple constructor. So lowering tries to resolve the bare self typeFieldName(written without itsconst N), which kicks off anE0107 "missing generics"cascade pointing deep into macro code. ButFieldName::len(..)is just an associated fn, not a constructor, so lowering it like aTupleCallwas wrong in the first place. See #157152.Only an enum can host a tuple-variant ctor, so for any other self type that can't (struct, union, primitive, foreign type) the call has to be an assoc fn and needs wrapping in
const { ... }. We catch those from the self type's resolution before lowering it and emit the existing "complex const arguments must be placed inside of aconstblock" error, which is the message you'd want anyway. Enums, aliases,Selfand type params get left alone since they might resolve to an enum. tbh the bare generic enum case (Option::Some(0)) still E0107s, and imo that's better as a follow-up since catching it needs the variant type before lowering. Tests cover struct/union/primitive/foreign plus the wrapped forms that compile, and I checked it against the realtracing0.1.44 crate too.fwiw just the code changes and tests were implemented with AI help and I verified/reproduced/tested everything locally before sending to remote.